This application claims priority of German Application Serial No. 101 12 024.9, filed Mar. 9, 2001, the complete disclosure of which is hereby incorporated by reference.
a) Field of the Invention
The invention is directed to an arrangement and method for generating a plurality of optical axes which are oriented in a defined manner relative to one another in which the directions of the optical axes are defined by the reflection angles of a light bundle at plane mirror surfaces arranged in different ways. It is suitable particularly for the production of laser plummets with a plurality of orthogonal axes and similar measurement instruments for the construction industry, but also offers many possible applications for aligning beam paths to be divided in a desired way in optical precision measurement instruments.
b) Description of the Related Art
Table systems and frame systems are known generally from the prior art for mirror adjustments. These table and frame systems which serve as supports for mirror surfaces are actuated mechanically by adjustment screws or piezo-electrically when the desired beam path of a light bundle is directed for the first time (or after repeated readjustments) to a target point by switching on the light sources being used. This procedure is likewise common in laser plummets for the construction industry, wherein the type of beam splitting and beam orientation is solved in different ways.
U.S. Pat. No. 4,912,851 discloses a level/plumb indicator in which the exact 90-degree orientation of a horizontal exit beam relative to the original vertical direction of the collimated laser beam is achieved by a two-mirror orthogonal reflector (penta prism). The vertical direction is generated by swiveling the reflector out of the laser beam. This solution has the decisive disadvantage that the two orthogonal exit beams are only available alternatively.
A similar portable laser device for orientation purposes is described in U.S. Pat. No. 5,144,487 in which (up to five) exit beams can be provided simultaneously in vertical, horizontal and orthogonal direction in that collimated light from a laser diode is split into a corresponding number of exit beams through an optical system. A projection unit comprising a laser diode, collimator and optical system is suspended in pendulum fashion such that at least one beam is oriented horizontally and other beams are oriented vertically or at right angles thereto. For purposes of beam splitting, the optical system contains at least one partially reflecting mirror which must be exactly adjusted, wherein small indicators are provided by the manner in which the partially reflecting mirror is oriented in an exactly reproducible manner, requiring a time-consuming final adjustment with reference to the target marks.
Another solution to the set of problems in multiple-axis laser sighting instruments is known from U.S. Pat. No. 6,005,716. In this case, the elliptic beam shape typical of laser diodes is deliberately used to direct the collimated elliptic light bundle in three adjacent circular bundles to three mirrors which are arranged directly next to one another in a plane and which are variously inclined by 45xc2x0 in three different directions, the middle mirror being partially transparent. This results in four orthogonal beam bundles. A fifth beam is added by inserting another partially reflecting mirror in the beam path of the beam reflected at the first partially reflecting mirror and reflects the beam bundle in the opposite direction. The different intensity of the orthogonal bundles resulting from the multiple division of individual beam bundles is disadvantageous. Further, the orientation of the individual mirror surfaces in this solution is also still time-consuming and this patent indicates neither the manner of holding the mirrors nor the procedure for suitable adjustment.
It is the primary object of the invention to find a novel possibility for generating a plurality of optical axes oriented in a defined manner relative to one another using plane mirror surfaces which allows desired accurate orientation of the optical axes independent from manufacturing tolerances of the components for holding the mirrors and a simple and stable final adjustment.
According to the invention, in an arrangement for generating a plurality of optical axes oriented in a defined manner relative to one another in which the optical axes are defined by the reflection angles of a light bundle at plane mirror surfaces arranged in different ways, the above-stated object is met in that the plane mirror surfaces are arranged on the section face of spherical segments, wherein every spherical segment always includes a spherical cap and a plane circle face and the axis of symmetry of the spherical segment extended beyond the circle face is a mirror surface normal, in that every spherical segment is embedded with its spherical cap in a recess of a base body, wherein the recess has a center axis, which is essentially adapted to the direction of the mirror surface normal required for the orientation of the optical axis, and an outside surface, and there are contact points between the spherical cap of the spherical segment and the outside surface of the recess, which contact points constitute an invariable pattern of contact points which is not dependent on the orientation of the mirror surface, and in that the spherical segments are rigidly fixed in the recesses of the base body, at least at the contact points, by means of a connection layer, wherein the plane mirror surfaces can be adjusted with the desired degree of accuracy prior to the final fixing of the connection layer corresponding to the optical axes to be aligned.
Every spherical segment is advisably provided with a mirror layer on its plane section face.
In order to limit the reflected light bundle in a defined manner, it is advantageous when the section face is covered by a mirror layer, wherein a sharply defined edge area is provided as a diaphragm. The mirror layer is preferably vapor-deposited on the section face. The edge area provided as diaphragm can be excluded from the vapor deposition or may be coated subsequently in addition. The spherical segments which carry the mirror surfaces are advisably half-spheres for reasons of simple manufacture. However, one-quarter spheres to three-quarter spheres may also be useful, depending on the needed size of the variance range of the angle for orienting the mirror surface.
The recesses for receiving the spherical segments in the base body are conical in one preferred variant; in this case, the invariable pattern of contact points between the outside surface of the conical recess and the spherical cap of an embedded spherical segment is a closed circular line.
It is also possible for the recesses to be shaped as regular pyramids, wherein the invariable pattern of the contact points would ideally be the corner points of an n-angle, when n is the quantity of lateral surfaces of the pyramid. Concretely, however (for reasons of manufacturing tolerances of n-sided pyramid-shaped recesses), the pattern of the contact points is a plane pattern with fewer than n corners, so that actually only the three-sided pyramid is useful for safely preventing tilting movements when orienting the spherical segments in the recess of the pyramid-shaped recesses. The points of contact with the spherical cap of the spherical segment which are located on a surface line of the lateral surfaces of the three-sided pyramid-shaped recess, even when deviating from the ideal shape of a regular pyramid, constitute a virtually equilateral triangle, but in any case a constant triangle representing a definite three-point bearing for the spherical cap.
For every optical axis to be aligned, the base body should advisably have a suitable surface portion for arranging the above-mentioned recess, wherein the surface normal of every such surface portion in the area of the recess should be essentially adapted as far as possible to the required direction of the mirror surface normals for orientation of the optical axes. This step facilitates access to the mirror surfaces during adjustment.
In order for a plurality of beam bundles to be oriented in desired manner within a plane orthogonal to the direction of the incident light bundle, the base body is preferably a cone, wherein the recesses can be introduced, always vertically, in the outside surface of the cone so as to be distributed in a desired manner.
In order to orient a plurality of beam bundles in different optical axes which are arranged relative to one another in a manner (usually regular) known beforehand, a base body with plane surfaces is advantageously used, wherein the plane surfaces are so aligned with respect to their position relative to an incident light bundle that they are again essentially parallel to the mirror surfaces to be arranged subsequently.
For purposes of an even distribution of a plurality of beam bundles within a plane orthogonal to the direction of the incident light bundle, the base body can advisably be a pyramid with n sides, where n is the quantity of beam bundles whose optical axes are to be aligned in a plane. When there are four beam bundles which are to be oriented within a plane and which are to be orthogonal to the direction of the incident light bundle and relative to one another, the base body is then advantageously a straight-line square pyramid.
When the surface portions at the base body for arranging the recesses are plane surfaces, this offers another shape possibility for the recesses. Cylindrical recesses are also suitable in this case, wherein the cylindrical recess has a diameter smaller than that of the associated spherical segment, so that the invariable pattern of the contact points is a circle at the upper edge of the cylindrical recess.
For simultaneous illumination of all of the mirror surfaces located on the outside surface of the base body, a light source is advisably provided which has a collimated light bundle extending symmetrically along the axis of symmetry of the base body, wherein the light source is arranged above the tip of the pyramid-shaped or conical base body. The same result is achieved when a light source is arranged below the outside surface of the base body, wherein the base body has a central symmetric opening through which the beam bundle of the light source is directed and a reflecting collimator which reflects the beam bundle proceeding from the light source onto the mirror surfaces in a collimated manner is arranged above the tip of the base body.
When the collimator is a collimator objective for collimating incident light for both transmission and reflection, there is the further advantage that, apart from the light bundles which are reflected within a plane (and which may also be oriented orthogonal to one another), another output beam bundle is oriented orthogonal to the reflected light bundles. This configuration is particularly relevant for the 5-axis configuration of laser plummets described in detail in the following. The collimator objective preferably has a mirror layer on a lens surface, wherein the mirror layer has a window in the area of the optical axis of the collimator objective for transmitting a limited light bundle. The window for the transmitted light bundle can advisably have a circular opening or a square opening.
In order to generate five orthogonal optical axes (using the above-mentioned transmission/reflection collimator), the central symmetric opening in the interior of the (preferably pyramid-shaped or conical) base body expands in the area of the base surface into a larger cylindrical countersunk bore hole with a conical end, and the light source which is embedded in a spherical holder for adjustment of the radiating characteristic is rotatably mounted in this countersunk bore hole. In this way, the light source can be accommodated in a space-saving manner and adjusted simply.
In order to simplify manufacture of the base body with the central recess, which is advisable for technical reasons relating to illumination, the base body can also be a truncated cone or truncated pyramid, wherein the opening is located between the top surface and the base surface so that a central portion of the light bundle proceeding from the light source can pass through unimpeded.
In order to align six light bundles in six directions orthogonal to one another (6-axis plummet), the base body advantageously comprises two congruent partial bodies with plane base surfaces. In this case, the partial bodies are arranged along a common center axis, have an outside surface which is inclined relative to the base surface and which is provided for introducing three recesses for the reflecting spherical segments, these recesses being evenly distributed about the common center axis of the partial body, and have base surfaces which are located opposite one another in a parallel manner and which are connected with one another in such a way that every two recesses situated in different partial bodies have center axes along one and the same straight line, and the optical axes of the reflected light bundles of all reflecting spherical segments have a common virtual point of intersection in the center of the assembled base body. Further, the mirror surfaces of the spherical segments in every partial body are illuminated by a light source having a collimated incident light bundle along the common center axis of the partial bodies.
The two-part base body preferably comprises two rotationally symmetric partial bodies with plane base surfaces. The partial bodies are preferably two cones or spherical segments. However, the base body can also comprise two three-sided pyramids whose parallel base surfaces are rotated by 60xc2x0 relative to one another about the common center axis of the partial bodies.
For advantageous illumination and suitable enclosure of the optical components for the 6-axis plummet configuration described above, a cube-shaped housing is advisably arranged around the base body, wherein the base body is positioned with its center axis along a body diagonal of the cube and point-symmetric with respect to the center of the cube, and two opposed, incident, collimated light bundles are provided along said body diagonal for illuminating the mirror surfaces of a partial body of the base body, wherein the mirror surfaces of every partial body are so aligned that each light bundle reflected by the mirror surfaces of a partial body traverses orthogonally and centrally one of the cube surfaces adjacent to the incident light bundle.
In a method for generating a plurality of optical axes that are oriented in a defined manner relative to one another, in which a reflected light bundle is generated from a collimated incident light bundle proceeding from a light source by means of the orientation of adjustable plane mirror surfaces, wherein the direction of the optical axes is adjusted by means of the reflection angle of the respective mirror surface relative to the incident light bundle, the object of the invention is further met by the following steps:
producing carrier bodies for mirror surfaces, wherein spheres are divided into spherical segments by plane cuts, resulting in spherical segments with a spherical cap and a circular surface,
arranging a mirror layer on the circular surface of the spherical segments, wherein the axis of symmetry of the spherical segment above the mirror surface is a mirror surface normal with respect to the optical axis to be aligned,
producing a base body, wherein a recess with a center axis and a non-spherical outside surface is so introduced in the surface of the base body for every optical axis to be aligned that the center axis of the recess is adapted at least approximately to the direction of the mirror surface normal required for the orientation of the optical axis, and the shape of the recesses is selected in such a way that the spherical segment is supported so that it is not displaceable but is rotatable about the center of curvature of the spherical cap,
arranging a connection layer on at least one of the surfaces of the spherical cap and recess, wherein the connection layer is used for subsequent rigid fixation of the two surfaces,
embedding the spherical segments with their spherical caps in the recesses of the base body,
aligning the different mirror surfaces by means of a master template by which the desired orientations of the optical axes are effected through alignment surfaces, and
fixing the reflecting spherical segments in the area of the contact points between the spherical cap of the spherical segment and the outside surface of the recess through rigid connection by means of the connection layer.
In particular, this method ensures a reproducible alignment of optical axes which are predetermined in a defined manner.
The recesses are advantageously introduced into the base body conically through countersunk bore holes and the spherical segments are fixed along a circular line of contact points at the conical outside surface of the recess.
However, in the case of plane surface parts of the base body, the recesses can also be introduced in the base body through cylindrical bore holes with a diameter that is smaller than the circular face of the spherical segment and the spherical segments are fixed to the upper edge of the cylindrical outside surface of the recess along a circular line of contact points.
Another way of introducing suitable recesses in the base body consists in producing the base body while simultaneously forming three-sided pyramid-shaped recesses, wherein the spherical segments are fixed around a contact point to each of the outside surfaces of the pyramid-shaped recess by the spherical cap.
In order to fix the spherical segment in the recess, a glue is advantageously applied at least at the contact points on one of the surfaces of the spherical cap or outside surface of the recess. The application of glue is advisably simplified by dipping the spherical cap in the glue.
In this respect, it is advantageous to apply a glue which is cured through application of energy after the spherical segments are adjusted. A glue which hardens by means of UV illumination and which is cured by a UV light source from the underside of the spherical segments through an access to the recesses which is arranged centrally in the base body is best suited for this purpose.
In another advantageous variant, at least the points of contact between the surfaces of the spherical cap and recess are provided with a coating which can be melted by the application of energy and which is then melted subsequent to the adjustment of the spherical segments.
Another step for fixing consists in that at least areas around the contact points of the surfaces of the spherical cap and recess are provided with a metallic coating, wherein the metallic coatings of both surfaces are melted together by laser soldering.
During adjustment, a maximum of three alignment surfaces are brought into contact with the provided mirror surfaces simultaneously by means of the master template for aligning the mirror surfaces before the mirror surfaces that are aligned in this way are deliberately made to rigidly connect the contact points by means of the connection layer introduced between the associated surfaces of the spherical cap and recess. In this way, a highly precise (definite) alignment of the mirror surfaces is ensured by a three-point contact of the template.
In order to align more than three mirror surfaces relative to one another, every additional mirror surface is adjusted and subsequently fixed by including two mirror surfaces which are already fixed.
The solution (arrangement and method), according to the invention, makes it possible to generate a plurality of optical axes oriented relative to one another in a defined manner by using plane mirror surfaces which can be aligned with any desired accuracy regardless of the manufacturing tolerances of the components for holding the mirrors and permit a simple and stable final adjustment of the mirror surfaces.
The invention will be described more fully in the following with reference to embodiment examples.